Stroke is the leading cause of severe, long-term disability among older adults in the United States. Nearly one third of stroke survivors have chronic hemiparesis. One of the most frequently persisting consequences of stroke is impaired hand function. The long-term objective of this research program is to develop an implanted neuromuscular electrical stimulation (NMES) neuroprosthesis that enables stroke survivors to use their paretic arm and hand again to perform activities of daily living. This exploratory study proposes to implement in two chronic stroke survivors (>6 months post-stroke) a neuroprosthesis that has previously been successfully implemented in tetraplegic spinal cord injury patients. The specific aims are to establish the feasibility of implementing the system in stroke survivors and to evaluate the effect of the neuroprosthesis on upper extremity motor impairment and activity limitation. The participants will undergo a surgical procedure in which the neuroprosthesis will be implanted. The implanted components include a multi- channel stimulator-telemeter, stimulation electrodes, and EMG-recording electrodes. The stimulating electrodes will be implanted on paralyzed upper extremity muscles. The EMG-recording electrodes will be implanted on upper extremity muscles of which the subject retains voluntary control. The individual will control their stimulated arm and hand movements by making particular muscle contractions. Special attention will be devoted to creating control strategies that are intuitive to the subjects and do not require unnatural movements or muscle contractions. The post-surgical course includes 3-4 weeks of immobilization, then 4-6 weeks of muscle strengthening with stimulation, followed by a two-week period of system customization and training. Feasibility of system implementation and effectiveness will be evaluated with assessments of technical performance and safety and clinical outcomes, which will be made at 3, 6, and 9 months after the training period. The clinical assessments will include measurements of upper extremity motor impairment and activity limitation with and without using the neuroprosthesis, which will be compared to baseline assessments. The neuroprosthesis is expected to enable the users to perform bimanual tasks that cannot be independently achieved otherwise. The successful completion of this study will: a) demonstrate the feasibility of an implanted upper extremity neuroprosthesis for hemiplegic stroke survivors, b) provide valuable information for improving the technology so that its applicability in stroke may be defined and expanded, c) provide an initial estimate of the effect of the neuroprosthesis on motor impairment and activity limitation, and d) generate pilot data to be used to design an R01 efficacy trial.